A constant-speed control apparatus for maintaining a set vehicle speed without operating the accelerator pedal is disclosed as TOKKAISHO-61-271132 in the Japanese Official Gazette. The equipment in the gazette shows a structure which can be installed on a vehicle having no constant-speed equipment without rebuilding the accelerator and the intake throttle valve of the vehicle.
The constant-speed apparatus includes the type having an actuator cooperable with the accelerator to open/close the intake throttle valve up to a specified opening position and prevent the valve from returning to its fully closed position to maintain the set vehicle speed.
In the above constant-speed (or cruise control) apparatus, however, when the constant-speed control is disengaged, the depressed accelerator pedal is quickly returned to its fully extended position by the accelerator-pedal return spring, and the intake throttle valve is quickly returned to its fully closed position. This occurs because, when the constant speed control apparatus is disengaged, prevention of the intake throttle valve from returning to the fully closed position is immediately cancelled. Therefore, the accelerator lever impacts with a stopper with a large force and produces a large impact noise, causing the operator to feel uncomfortable. There is also the disadvantage that the service life of the constant-speed apparatus is shortened because the above quick return operation causes a large reaction force to be transmitted to the drive installed on the actuator which controls the opening/closing of the intake throttle valve.
In addition, a cushion is conventionally installed to decrease impact noise. However, the noise is not adequately decreased by the cushion and the cost is increased due to increase of components.
Therefore, one purpose of the invention is to provide a constant-speed (or cruise control) apparatus having an actuator cooperable with the accelerator to open/close the intake throttle valve up to the specified opening position to maintain the set vehicle speed, which apparatus is capable of decreasing impact noise produced by the accelerator due to the rapid return of the intake throttle valve to the fully closed position (and the corresponding rapid return of the accelerator lever and its impact with a stopper) when control of the set vehicle speed is cancelled.
Another object of the present invention is to provide a cruise control apparatus, as aforesaid, which is also capable of an increased service life while avoiding an increase in cost.